On Mon, Sep 03, 2018 at 07:13:16PM +0300, Arseny Maslennikov wrote:
> Signed-off-by: Arseny Maslennikov <ar@cs.msu.ru>
> ---
>  drivers/infiniband/ulp/ipoib/ipoib_main.c | 38 +++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> index 30f840f874b3..7386e5bde3d3 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> @@ -2386,6 +2386,42 @@ int ipoib_add_pkey_attr(struct net_device *dev)
>  	return device_create_file(&dev->dev, &dev_attr_pkey);
>  }
>
> +/*
> + * We erroneously exposed the iface's port number in the dev_id
> + * sysfs field long after dev_port was introduced for that purpose[1],
> + * and we need to stop everyone from relying on that.
> + * Let's overload the shower routine for the dev_id file here
> + * to gently bring the issue up.
> + *
> + * [1] https://www.spinics.net/lists/netdev/msg272123.html
> + */
> +static ssize_t dev_id_show(struct device *dev,
> +			   struct device_attribute *attr, char *buf)
> +{
> +	struct net_device *ndev = to_net_dev(dev);
> +	ssize_t ret = -EINVAL;
> +
> +	if (ndev->dev_id == ndev->dev_port) {
> +		netdev_info_once(ndev,
> +			"\"%s\" wants to know my dev_id. "
> +			"Should it look at dev_port instead?\n",
> +			current->comm);
> +		netdev_info_once(ndev,
> +			"See Documentation/ABI/testing/sysfs-class-net for more info.\n");
> +	}
> +
> +	ret = sprintf(buf, "%#x\n", ndev->dev_id);
> +
> +	return ret;
> +}
> +static DEVICE_ATTR_RO(dev_id);
> +

I don't see this field among exposed by IPoIB, why should we expose it now?

> +int ipoib_intercept_dev_id_attr(struct net_device *dev)
> +{
> +	device_remove_file(&dev->dev, &dev_attr_dev_id);
> +	return device_create_file(&dev->dev, &dev_attr_dev_id);

Why isn't enough to rely on netdev code?

> +}
> +
>  static struct net_device *ipoib_add_port(const char *format,
>  					 struct ib_device *hca, u8 port)
>  {
> @@ -2427,6 +2463,8 @@ static struct net_device *ipoib_add_port(const char *format,
>  	 */
>  	ndev->priv_destructor = ipoib_intf_free;
>
> +	if (ipoib_intercept_dev_id_attr(ndev))
> +		goto sysfs_failed;
>  	if (ipoib_cm_add_mode_attr(ndev))
>  		goto sysfs_failed;
>  	if (ipoib_add_pkey_attr(ndev))
> --
> 2.19.0.rc1
>